Process and installation for the treatment of fermentiscible industrial residuary waters



June'4, 1957 Y. vRxGNAuD 2,794,778

PROCESS AND INSTALLATION FOR THE TREATMENT OF FERMENTISCIBLE INDUSTRIAL RESIDUARYWATERS Filed Oct. 2, 1953 2 Sheets-Sheet 1 June 4, 1957 Y. VRIGNAUD 2,794,778

Y ?ROCESS AND INSTALLATION FOR THE TREATMENT OF FERMENTISCIBLE INDUSTRIAL RESIDURY WATERS Filed 001'.. 2, 1953 2 Sheets-Sheet 2 PROCESSfAND INSTALLATIGN FOR THE TREAT-- QF FERMENTISCIBLE INDUSTRIAL RE- SDUARY: WATERS Yves Vrign'aud;` Paris, France,` assignor to Socit Anonyme dite: Fromageries'B'el, Paris,`Y France Appleation-Gctober, 1953, Serial No'. 383,859

Clainslpriority, application France November 5, 19525 Numer'ous'f-processesf havealready been proposed J for the treatment of industrial residuary Waters andi particularly of residuary watersf'r'om the milkindustries; ithas been proposed,` inparticular, heretofore to treat said waters byf anaerobic treatment, ooculation andA separation, possibly after a first preliminary separation offthef heaviest solidelementsfin' suspension. None of theseformer processes, however, has proven entirely satisfactory in'- use; particularly for treatingresiduary waters from the milk industries.

It was found, according to the presenti invention, that an-excellent-fresult-could:be obtained'inla'n industrial manner by' a'l treatment of-theabove-rnentionedtypin which the waters are subjected toaflrst operation iny a closed circuit, a'lo'cculation agentlbeing added to them towards the end 0f this-first aeration, are than allowed to'V re'st-` for* allowing fiocculationto take'fplace andl the Waters to clarify, then subjected to'asec'ond'-y closed? cir-2 cuit'r aeration,- arid' finally subieetedk tofia-nat separation whichsto'p's th'e muds and?v allo'Wsthe purified waters:V tov In some'-l cases,-tl1`is= process may'y b'eiirlprovedV by subjecting-thewaters t'o` be pu'riiied t'o a preliminary puri'- cation; thus,rin particular,an aeration-range may'convenientlybe' immersed in the' receiving tank and the' aeration' may beco'ri'tinu'edA as lon'gasitherefisany residu-l The main aratin may bei effected-'f inside' treatingY tanks; Ito eect-an` aeration system-may beimmersed in' saidtanks; as` for' example perforated; tubes, porous tubes, porous: plate'slorany' other devicemaking itipcssible to diffuse air through the mass in circulation.

The process according to the' invention and the installation foriV the application of saidprocessi have, with'.

respect to processes and installations known ati present acomplete' se't'of technical-advantages, a s'etwhich could' ments such' as fats; the latter too often' clogging. thepurifying mechanism and spreading the pollution in time and in space.

3. The substances in solution capable of creating an acidity momentarily clogging the purifying in the processes wbiclidov not strictly eliminate anaerobia are destroyed or eliminated. They-cannot, therefore, jeopardize the biological purification Work or be the causes of delayednui'sances.

The residuary waters which have been treat'edi by,v theV process according to the present invention have lost their fermentiscible and reducing nature, as well as their potential of transformation of the ionic energy of the re- ICC ceiving medium; their bacterial charge is very low-andV thel degradation. products ofi the yorganic materialsv are nontoxic;-V

The waters thusfpuritied: may be dumped in water streamsfevenr ofsmall rate' of flow, orover lands'fwithoutcausingrany troublesro-nrtheA fauna, flora, ground or underground sheets.

NotV only is the purification of Waters eicient, butV theVt installation accordingk to the process has advantages-ot.V

its-own:

l. A small bulk,` owing to the absence of stocking.

2. No evil smell-, due` to operating under conditions which-'eliminate strictly allV anaerobic fermentations.

3. Extraction muds are of small volume.

4;- The eiciency of the installation is notfjeopardized byy aV long 'period offoperation or by the `introducing-of-` an abnormal fouling load.

5I The necessary lequipment can' rapidly' be assembled or disassembled and installed again without 'any important civil-engineering Work. Beingof small bulk, it canbe mounted' inside the-factory. The initial installation costs are substantially lowerthan those which would bevrequired, for an-equalfouling load, by the installation of a conventional biochemicalpuriication. station. The'puritying station-being-easy'to control-may be entrusted to an personnel-which need' notv be'nurnerous nor particularly skilled, Wliiehdiminishes still further the operating costs;

Byway of non-linlit'ativeV example, there is describeclzl herein after the installation and operation according to the invent-ion, of' a station for treating theresiduary: waters fi'onl-anri'ndustria'lY dairy, the latterI terrn applying to anyL factory -for'lth'e transformation, storing-or conditioning-of' milk and its derivatives.

The appended drawing shows, by way'of example, an

installationfor the' putting inapplication of the process according to the' present invention.

Figures l-and Z'areviews respectively in elevation and. in plan.-

Figures 3 andi 4 are alsoI views, respectively in plan-kr andin transverse section, on a larger scale, of one-of the," elements-shown in the previous gures.

Thewater arriving from the sewer through, the duct 1 hows-intov the' suctionl sump 2' whence, through a. strainer 23', tliepump 3v can send it', through conduitszl or 5, towards oneofthe treating tanks 6 or 7', according tothe position of the cock 8; acentri-fugal separator 9is insertedon the sectie-n10; common to conduits 4 'and'.S.v

To each tank 6"'arldi7, the number ofrwhich mayvary` according to the importance ot'.` the installation and;- the.V volume of waters to be treated, a circulation pump 11, 12 is associated, and an aerator 13; 1.4 supplied by a blown aii conduit 24, 25 connectedwith the air compressor Z6,- so that the water ows in a closed circuit fromthe tank, through the conduit 15, 16,.throughvthe` aerator I3, 14' and back to the tank.

The waters may-'then be taken again from theztanks 6 and7 through conduits 17 or 18- according to the' posiitions of the cocks 22, the pumps 31V and-29, the conduitr 10, the separator 91 and sent backl either in' a close'dzcircuit' toltlie' tanks 6 o1' 7, or through the conduit: 20 to the sewer 21 for the evacuation of purifiedA Waters.

The installation is completed byv all thernecessary cocks4 222, ducts 27: for the overflowsI from the tanks 6 and'. 7' andv al conduit 28` for the return of the output of they separator 9 to the sump 2 with. a viewl to a new treatment in case it should be' found that, i'orV one reason or another, the purifying is insutiicient.

The operation is aslfollows:

After a preliminary separation, the various tanks are. iilled alternately.

When a tank is full, the residuary water it contains is put in circulation on the corresponding aerating appa- Patenfed Jnei 4,. 1957' 3 ratus which diffuses air through the mass and sends the aerated water back to the tank; the rst operation lasts about two hours, the water flows a second time through the aerator, for a variable time, never less than four hours.

Towards the end of the first operation of circulation and aeration, the chemical products for accelerating ilocculation are introduced. These chemical products may consist of a mixture of iron and calcium salts. A usual proportion for residuary waters from a modern cheese dairy making pressed paste cheese and using also, for other purposes, a volume of lacto-serum equal to 75% of the volume of milk treated is 600 cm.3 of a solution of ferrie chloride at 60 B., 400 grams of unslaked limed per cubic meter of treated water.

The iron salts are first introduced, then ten minutes later, the lime, previously slaked, in solution in a few litres of water.

At this stage of the treatment, the circulation ensures a good distribution of the occulating products throughout the mass of liquid.

After ya quarter of ian hour, the circulation is stopped and the liquid allowed to stand for an hour. The tanks, preferably, have conical bottom, with a fairly small apex angle, so that the muds may be rapidly evacuated, either toward the aeration circuit or toward the circuit for centrifugal separation. Flocculation is very abundant, and the clarifying of the liquid very rapid; at this stage, however, the clear liquid is still fermentiscible.

'The circulation pump is restarted and the contents of the tank are again circulated through the aerator for a duration of six to twelve hours, according to the fouling load.

Circulation is then stopped and the muddy output is sent back to the centrifugal separator which stops these muds and allows the purified liquid to flow to the evacuation sewer.

In the variant shown in Figures 3 and 4, inside the suction sump 2 and at its lower portion, ranges of perforated tubes 31 are arranged,V longitudinally, and are supplied with compressed air through the conduit 32; the raw spent waters arrive at the receiving tank through the conduit 1 and they are sucked, through the conduit 34, protected by the strainer 23, by the pump 3 which directs them, in particular, towards the treatment tanks.

There will be given hereinafter a practical example of a treatment of residuary waters from the milk industries.

The water from the collecting drain of the plant is received in a cement vat, after passing through a iilter capable of stopping large impurities.

The effluent is immediately pumped and sent into one of the process tanks; aeration begins immediately by a circulation of the residuary water in the aerator circuit; it is continued for the whole duration of the filling and, in addition, two hours after the end thereof.

At that moment, the pH is summarily determined and iron salts are added, preferably in the shape of sulphate; the amounts of iron are all the higher as the pH is higher; they Vary normally between 20 and 35 kg. for a tank containing 30,000 litres of etliuent. The eluent being in circulation on the aerators, the mixing of the iron salts is rapid. In order to facilitate this operation, the sulphate is used in a concentrated solution.

The lime is then sent into the tank in a su'icient proportion for bringing the pH back to a value higher than pH 7, but which should never exceed pH 8. After the admixture of lime milk, the circulation is kept up for to 20 minutes, for ensuring a homogeneous distribution.

The circulation is then stopped for allowing the flocculation to take place in the best conditions. As soon as the latter is ended and the flocculation product has settled, which requires from 40 to 60 minutes, the oircnlation is reestablished over the aerators for two hours ens/mrs 4 at least. At that stage, the sludge formed is oxidized and its colour makes it possible to see when the treatment is nished. The sludge, which was blue, or green, becomes brick red. To reach thatA stage it is Sometimes necessary to aerate for more than two hours, which does not alter anything in the initial process.

When the oxidizing is deemed suflicient, the water and its occulation product are sent to the centrifugal separators where the sludge settles immediately and the clear eiuent is sent to the sewer network or to the river.

The waters from cheese factories, for instance, are received with D. B. 0.5 of 1200 to 5-6,000 as in all cases, they contain some lactose, more or less. The latter always arrives with serum, i. e. at the times corresponding to the work of the rennet and moulding shops. The residuary waters corresponding to these working hours undergo systematically a longer aeration in the iirst stage.

Practice, in a factory, makes it possible to know rapidly the peak load hours when a laboratory has not already done it.

The treated effluents arrive at very low D. B. 0.5, ot the order of 30 to 50, with initial D. B. 0.5 not exceeding 4000, which means that the results are very satisn factory.

This process is applied regularly in the cheese factory at Laumes (Cote dOr) and no polluting of the small trout brook is found, while previously all aquatic life has disappeared.

Y stand during occulation for about 1 hour, and the second aeration lasts a minimum of about 4 hours.

2. A process according to claim 5, in which the raw spent waters are subjected to a preliminary aerationV before said rst aeration.

3. An installation for the treatment of residuary waters comprising a single settling tank, a pump and a irst conduit connected to said settling tank for bringing the residuary waters to said tank, a closed circuit including said settling tank and comprising a pump and an aerator adapted to inject air through the waters circulated by said pump from and to said tank, a centrifugal separator, and a second conduit connecting the tank with the centrifugal separator and having an extension for evacuating theV purified waters issuing from the separator.

4. An installation according to claim 3 wherein said first conduit includes said centrifugal separator whereby the pump brings the residuary waters to the tank through the separator.

5. VA method of treating Waste waters from the milk industries and like fermentiscible industrial residuary Waters, by aerobic puriication, occulation and separation, which consists in the steps of circulating said waters in a closed circuit, effecting a rst aeration of said vwaters by injecting air therethrough as they are being circulated, adding a occulating agent substantially upon completion of said rst aeration, discontinuing said circulation and maintaining said waters still until said occulation has taken place and said Waters have been clarified, re-circulating said waters in a closed-circuit while subjecting said waters to another air injection as they are being circulated,

and nally effecting a centrifugal separation to retain the sludge and to separate the clean waters therefrom.

OTHER REFERENCES Trebler et al.: Sewage Works Journal, vol. 10, pp. 884- 886 (1938). 

3. AN INSTALLATION FOR THE TREATMENT OF RESIDUARY WATERS COMPRISING A SINGLE SETTLING TANK, A PUMP AND A FIRST CONDUIT CONNECTED TO SAID SETTLING TANK FOR BRINGING THE RESIDUARY WATERS TO SAID TANK, A CLOSED CIRCUIT INCLUDING SAID SETTLING TANK AND COMPRISING A PUMP AND A AERATOR ADAPTED TO INJECT AIR THROUGH THE WATERS CIRCULATED BY SAID PUMP FROM AND TO SAID TANK, A CENTRIFUGAL SEPARATOR, AND A SECOND CONDUIT CONNECTING THE TANK WITH THE CENTRIFUGAL SEPARATOR AND HAVING AN EXTENSION FOR EVACUATING THE PURIFIED WATERS ISSUING FROM THE SEPARATOR.
 5. A METHOD OF TREATING WASTE WATERS FROM THE MILK INDUSTRIES AND LIKE LERMENTISCIBLE INDUSTRIAL RESIDUARY WATERS, BY AEROBIC PURIFICATION, FLOCCULATION AND SEPARATION, WHICH CONSISTS IN THE STEPS OF CIRCULATING SAID WATER IN A CLOSED CIRCUIT, EFFECTING A FIRST AERATION OF SAID WATERS BY INJECTING AIR THERETHROUGH AS THEY ARE BEING CIRCULATED, ADDING A FLOCCULATING AGENT SUBSTANTIALLY UPON COMPLETION OF SAID FIRST AERATION, DISCONTINUING SAID CIRCULATION AND 